The present invention relates to a method for producing a stepped semi-hardened product having a joggle made of a fiber-reinforced composite, and a method for producing a preformed structure composed of the stepped semi-hardened product having a joggle and a simple shaped semi-hardened product.
Stiffened panels made of a fiber-reinforced composite (prepreg) are light in weight and high in strength, to have been widely used for automobiles, ships, aircrafts, etc. The stiffened panels are generally produced by placing members for a skin and stiffeners (stringers and frames) each made of a fiber-reinforced composite on a forming tool to prepare an assembly, and by adhesive-forming the assembly by heating under a pressure using a pressure bag, etc. It is preferred that members composing the stiffeners are arranged on a skin member as a semi-hardened preformed structure, and completely hardened with the skin member, from the viewpoint of weight-reduction.
FIG. 1 is a perspective view showing an example of the preformed structure. In a preformed structure 1 of FIG. 1, simple shaped semi-hardened products 2a and 2b are arranged at a predetermined interval as the stringer members, and joggles of stepped semi-hardened products 3a, 3b and 3c are piled on the simple shaped semi-hardened products 2a and 2b. Each semi-hardened products 2a, 2b, 3a, 3b and 3c has a T-shaped section of a base portion and a projecting portion, although they may have a section of C-shape, I-shape, etc.
Conventionally, the above-mentioned semi-hardened products have been produced by a method comprising the steps of: cutting fiber-reinforced composites many times to obtain desired lamination structures, respectively; laminating and forming the fiber-reinforced composites on a forming tool. However, this method necessitates complicated works, in particular, lamination of the fiber-reinforced composites on the forming tool is achieved by handwork to require much effort. Further, in the case of such a complicated shaped semi-hardened product that has a joggle, the above lamination is remarkably difficult, thereby failing to produce them with a uniform quality. Furthermore, in the case of producing a plurality of semi-hardened products, which have different shapes, lengths, etc., the above conventional method demands many forming tools for each products to increase production costs.
Accordingly, an object of the present invention is to provide a method for producing a stepped semi-hardened product having a joggle made of a fiber-reinforced composite, where the stepped semi-hardened product of uniform, high quality can be stably produced with reduced processes and production costs.
Another object of the present invention is to provide a method for producing a preformed structure utilizing the above method for producing a stepped semi-hardened product, which can produce the preformed structure with reduced processes and production costs.
As a result of intensive research in view of the above objects, the inventor has found that a stepped semi-hardened product of high quality can be stably produced with reduced processes and production costs by a method where a flat plate-shaped laminate is provided by laminating a plurality of sheets made of a fiber-reinforced composite beforehand, a simple shaped intermediate is prepared by forming the flat plate-shaped laminate, and an edge portion of the simple shaped intermediate is heated under a pressure. The present invention has been accomplished by the finding.
Thus, a method for producing a stepped semi-hardened product having a joggle in an edge portion according to the present invention comprises: the first process where a plurality of first sheets made of a fiber-reinforced composite are laminated to each other, heated under a pressure and cooled under a pressure to provide a first flat plate-shaped laminate; the second process where the first flat plate-shaped laminate is softened by heating, placed on a first forming tool and formed by cooling under a pressure to prepare a simple shaped intermediate; and the third process where an edge portion of the simple shaped intermediate is heated under a pressure to form the joggle.
The method for producing a stepped semi-hardened product of the present invention is suitable for producing such that having a T-shaped section.
In a method for producing a preformed structure of the present invention, the preformed structure is composed of a stepped semi-hardened product having a joggle and a simple shaped semi-hardened product each made of a fiber-reinforced composite,
the stepped semi-hardened product is produced by: the first process where a plurality of first sheets made of a fiber-reinforced composite are laminated to each other, heated under a pressure and cooled under a pressure to provide a first flat plate-shaped laminate; the second process where the first flat plate-shaped laminate is softened by heating, placed on a first forming tool and formed by cooling under a pressure to prepare a simple shaped intermediate; and the third process where an edge portion of the simple shaped intermediate is heated under a pressure to form the joggle,
the simple shaped semi-hardened product is produced by: the fourth process where a plurality of second sheets made of a fiber-reinforced composite are laminated to each other, heated under a pressure and cooled under a pressure to provide a second flat plate-shaped laminate; and the fifth process where the second flat plate-shaped laminate is softened by heating, placed on a second forming tool and formed by cooling under a pressure, and
the joggle of the stepped semi-hardened product is piled on the simple shaped semi-hardened product.
The method for producing a preformed structure of the present invention is suitable for producing such that composed of the stepped semi-hardened product and the simple shaped semi-hardened product each having a T-shaped section.